Optical bench subassembly having integrated photonic device

ABSTRACT

An optical bench subassembly including an integrated photonic device. Optical alignment of the photonic device with the optical bench can be performed outside of an optoelectronic package assembly before attaching thereto. The photonic device is attached to a base of the optical bench, with its optical input/output in optical alignment with the optical output/input of the optical bench. The optical bench supports an array of optical fibers in precise relationship to a structured reflective surface. The photonic device is mounted on a submount to be attached to the optical bench. The photonic device may be actively or passively aligned with the optical bench. After achieving optical alignment, the submount of the photonic device is fixedly attached to the base of the optical bench. The optical bench subassembly may be structured to be hermetically sealed as a hermetic feedthrough, to be hermetically attached to a hermetic optoelectronic package.

1. PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.16/372,377 filed on Apr. 1, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/077,816 filed on Mar. 22, 2016, which:

-   -   (1) claims the priority of U.S. Provisional Patent Application        No. 62/136,601 filed on Mar. 22, 2015;    -   (2) is a continuation-in-part of U.S. patent application Ser.        No. 13/861,273 filed on Apr. 11, 2013, which:        -   (a) claims the priority of U.S. Provisional Patent            Application No. 61/623,027 filed on Apr. 11, 2012,        -   (b) claims the priority of U.S. Provisional Patent            Application No. 61/699,125 filed on Sep. 10, 2012, and        -   (c) is a continuation-in-part of U.S. patent application            Ser. No. 13/786,448 filed on Mar. 5, 2013, which claims the            priority of U.S. Provisional Patent Application No.            61/606,885 filed on Mar. 5, 2012; and    -   (3) is a continuation-in-part of U.S. patent application Ser.        No. 14/714,211 filed on May 15, 2015, now U.S. Pat. No.        9,782,814, which:        -   (a) claims the priority of U.S. Provisional Patent            Application No. 61/994,094 filed on May 15, 2014, and        -   (b) is a continuation-in-part of U.S. patent application            Ser. No. 14/695,008 filed on Apr. 23, 2015.

These applications are fully incorporated by reference as if fully setforth herein. All publications noted below are fully incorporated byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to optical bench subassemblies,particularly optical fiber subassemblies based on optical benches, andmore particularly hermetic optical fiber feedthrough subassemblies basedon optical benches.

Description of Related Art

There are many advantages of transmitting light signal via optical fiberwaveguides and the use thereof is diverse. Single or multiple fiberwaveguides may be used simply for transmitting visible light to a remotelocation. Complex telephony and data communication systems may transmitmultiple specific optical signals. The data communication systemsinvolve devices that couple fibers in an end-to-end relationship,including optoelectronic or photonic devices that include optical andelectronic components that source, detect and/or control light,converting between light signals and electrical signals.

For example, a transceiver (Xcvr) is an optoelectronic module comprisingboth a transmitter (Tx) and a receiver (Rx) which are combined withcircuitry within a module housing, which is known in the art as apackage. The package may be hermetically sealed to protect its contentsfrom the environment. The transmitter includes a light source (e.g., aVCSEL or DFB laser), and the receiver includes a light sensor (e.g., aphotodiode (PD)). Heretofore, a transceiver's circuitry (e.g., includinga laser driver, trans-impedance amplifier (TIA), etc.) is soldered ontoa printed circuit board. Such a transceiver generally has a substratethat forms the bottom or floor of the package (either hermetic ornon-hermetic), and then optoelectronic devices such as lasers andphotodiodes are soldered onto the substrate. Optical fibers areconnected to the exterior of the package or fed through the wall of thepackage using a hermetic feedthrough (see, US20130294732A1, which hadbeen commonly assigned to the Assignee/Applicant of the presentapplication, and is fully incorporated as if fully set forth herein).

The end of the optical fiber is optically coupled to the optoelectronicdevices held within the housing. A feedthrough element supports theportion of the optical fiber through the wall opening. For a variety ofapplications, it is desirable to hermetically seal the optoelectronicdevices within the housing of the optoelectronic module, to protect thecomponents from corrosive media, moisture and the like. Since thepackage of the optoelectronic module must be hermetically sealed aswhole, the feedthrough element must be hermetically sealed, so that theelectro-optic components within the optoelectronic module housing arereliably and continuously protected from the environment.

For proper operation, an optoelectronic device supported on a printedcircuit board needs to efficiently couple light to an external opticalfiber. Some optoelectronic devices require single-mode opticalconnections that require stringent alignment tolerances between opticalfibers and the devices, typically less than 1 micrometer. This ischallenging especially for multiple fiber applications, where multipleoptical fibers need to be optically aligned to multiple optoelectronicdevices using an active optical alignment approach in which the positionand orientation of the optical fiber(s) is adjusted by machinery untilthe amount of light transferred between the fiber and optoelectronic ismaximized.

FIGS. 1A and 1B depict a hermetically sealed optoelectronic package 500,having a hermetic multi-fiber feedthrough 502, in which the hermeticfeedthrough 502 is actively aligned with the photonic device 504 mountedon a submount 506 supported by the floor of the package 500. In thisexample, the feedthrough 502 resembles the optical coupling devicedisclosed in US2016/0016218A1, which had been commonly assigned to theAssignee/Applicant of the present application, and is fully incorporatedas if fully set forth herein). The photonic device 504 may include aVCSEL array and/or PD array, which is supported on the package floor,e.g., via a submount 506 and a printed circuit board 508. The printedcircuit board 508 is populated with other electronic components andcircuits, and the package 500 may include several printed circuitboards. After assembling the photonic device 504/submount 506 and othercomponents into the package 500, the feedthrough 504 is inserted throughan opening 503 defined by a snout 50 on the sidewall of the housing 501of the package 500. The array of optical fibers 20 of an optical fibercable 21 is supported by the feedthrough 502, and are actively alignedwith the photonic device 504, to achieve the desired optical couplingefficiency between the photonic device and the array of optical fibers20. This process requires the photonic device 504 and associatedelectronics (not shown) to be preassembled into the package 500. Thephotonic device 504 is activated/energized to transmit/receive anoptical signal 22 to/from the array of optical fibers 20. Essentially,optical signals to/from the optical fibers 20 are optimally coupled tothe photonic device 504 when the signal 22 transferred between theoptical fibers 20 and the photonic device 504 is maximized. Thefeedthrough 502 is then soldered into the snout 50 at the packagesidewall of the housing 501 in the optically aligned state.

Active optical alignment involves relatively complex, low throughputprocesses since the VCSEL or PD must be energized during the activealignment process. Manufacturers of integrated circuits often haveexpensive capital equipment capable of sub-micron alignment (e.g. waferprobers and handlers for testing integrated circuits), whereas companiesthat package chips generally have less capable machinery (typicallyseveral micron alignment tolerances which is not adequate forsingle-mode devices) and often use manual operations.

The current state of the art is expensive due to the inclusion of apackage, excludes the use of common electronics and assembly processes,and/or often not suited to single-mode applications. The package is arelatively more expensive assembly (which includes expensive circuitcomponents, such as ICs, etc.) as compared to the hermetic feedthroughsubassembly. Given the required preassembly of components in the packageto support active optical alignment, and further given the activealignment and soldering process involve high risk steps towards the endof the overall packaging process, failure to achieve active alignmentbecause of defective components, which may be induced in the activealignment process, would lead to the entire package being discarded,including the photonic devices and other components already packagedtherein.

In addition, while VCSEL and PD components may be tested in a staticstate prior to assembly, however they cannot be tested in an operationalstate until assembled in the package along with the electronics to drivethese components. Accordingly, burn-in process (to identify earlier-lifecomponent failures under simulated load conditions) of the VCSEL and PDcomponents can only be conducted after assembly of these components intothe package. This would lead to further waste of packages (i.e., lowyield of packages) that are relatively more expensive module asassembled, as a result of defective but relatively inexpensive VCSEL andPD components. VCSEL and PD components are known to contribute to arelatively high number of failures of assembled packages.

A further failure mode leading to waste of assembled packages is causedby the relatively larger and more compliant structural loop (representedby dotted line L in FIG. 1B) that maintains optical alignment betweenthe photonic device and the feedthrough, as shown in FIG. 1B. The longstructural loop is more sensitive to thermal-mechanical deformations,which could render the package to stray outside of intended designspecification, thus resulting in failure mode.

What is needed is an improved structure to couple the input/output ofoptical fibers in optical alignment to optoelectroniccomponents/photonic devices, which improves throughput, tolerance,manufacturability, ease of use, functionality and reliability at reducedcosts.

SUMMARY OF THE INVENTION

The present invention provides an improved structure to facilitateoptical alignment of photonic device to an optical bench, whichovercomes the drawbacks of the prior art. The present invention combinesa photonic device with an optical bench in a subassembly, so thatalignment of the optical coupling of the photonic device with theoptical bench can be performed outside of the optoelectronic packageassembly.

In accordance with the present invention, the photonic device isattached to a base of the optical bench, with its optical input/outputin optical alignment with the optical output/input of the optical bench.

In one embodiment, the optical bench supports an optical component inthe form of an optical wave guide (e.g., an optical fiber). In a morespecific embodiment, the base of the optical bench defines an alignmentstructure in the form of at least one groove to precisely support theend section of an optical fiber. An optical element (e.g., a lens, aprism, a reflector, a mirror, etc.) may be provided in preciserelationship to the end face of the optical fiber. In a furtherembodiment, the optical element comprises a structured surface, whichmay be planar reflective or concave reflective (e.g., an asphericalmirror surface).

In one embodiment, the photonic device may be mounted on a submount,which is attached to the base of the optical bench in optical alignmentwith the optical bench. The submount may be provided with circuits,electrical contact pads, circuit components (e.g., a driver for VCSEL, aTIA for a PD), and other components and/or circuits associated with theoperation of the photonic device.

The photonic device may be passively aligned with the optical bench(e.g., relying on alignment indicia provided on the base of the bench).Alternatively, the photonic device and the optical bench may be activelyaligned by passing an optical signal between the optical waveguide inthe optical bench and the photonic device. The photonic device (e.g., aVCSEL and/or PD) can be activated to allow for active alignment with theoptical waveguide (e.g., an optical fiber) supported in the opticalbench, without relying on the other components within the package. Afterachieving optical alignment, the submount of the photonic device isfixedly attached to the base of the optical bench.

The base of the optical bench is preferably formed by stamping amalleable material (e.g., metal), to form precise geometries andfeatures of the optical bench. The optical bench subassembly can bestructured to be hermetically sealed.

In another embodiment of the present invention, the optical bench isstructured to support multiple waveguides (e.g., multiple opticalfiber), and structure reflective surfaces (e.g., an array of mirrors),to work with an array of photonic devices (VCSELs and/or PDs) mounted ona submount.

The present invention preassemblies optical elements and components andphotonic devices precisely in an optical bench subassembly, prior toassembling into the larger optoelectronic package. The subassembly canbe functionally tested, including burn-in tests, in a subassembly level,outside of a optoelectronic package, thus reducing waste of moreexpensive optoelectronic packages arising from early failure in thephotonic devices installed therein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of theinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings. In the following drawings, like referencenumerals designate like or similar parts throughout the drawings.

FIG. 1A illustrates a hermetic optoelectronic package including ahermetic optical fiber feedthrough; FIG. 1B is a sectional view takenalong line 1B-1B in FIG. 1A.

FIG. 2A illustrates an optical bench subassembly in the form of ahermetic feedthrough, including an integrated photonic device, inaccordance with one embodiment of the present invention; FIG. 2B is asectional view taken along line 2B-2B in FIG. 2A, shown as installed ina hermetic optoelectronic package.

FIG. 3A is an expanded view of the optical bench in the optical benchsubassembly in FIG. 2, in accordance with one embodiment of the presentinvention; FIG. 3B is an assembled view of the optical bench.

FIG. 4A is an expanded view of the optical bench in the optical benchsubassembly, in accordance with another embodiment of the presentinvention; FIG. 4B is an assembled view of the optical bench.

FIG. 5 illustrates an alternate embodiment of a submount for thephotonic device in the optical bench subassembly.

FIGS. 6A to 6C illustrate the sequence of assembly of a hermeticoptoelectronic package, wherein FIG. 6A depicts assembly of a photonicdevice assembly; FIG. 6B depicts assembly of the photonic deviceassembly to the optical bench and active alignment; FIG. 6C depictsassembly of the hermetic optoelectronic package.

FIG. 7 illustrates the hermetic feedthrough as installed in the hermeticoptoelectronic package.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is described below in reference to various embodimentswith reference to the figures. While this invention is described interms of the best mode for achieving this invention's objectives, itwill be appreciated by those skilled in the art that variations may beaccomplished in view of these teachings without deviating from thespirit or scope of the invention.

The present invention provides an improved structure to facilitateoptical alignment of photonic device to an optical bench, whichovercomes the drawbacks of the prior art. The present invention combinesa photonic device with an optical bench in a subassembly, so thatalignment of the optical coupling of the photonic device with theoptical bench can be performed outside of the optoelectronic packageassembly.

In accordance with the present invention, the photonic device isattached to a base of the optical bench, with its optical input/outputin optical alignment with the optical output/input of the optical bench.Various embodiments of the present invention incorporate some of theinventive concepts developed by the Assignee of the present invention,nanoPrecision Products, Inc., including various proprietary includingoptical bench subassemblies for use in connection with optical datatransmissions, including the concepts disclosed in the patentpublications discussed below, which have been commonly assigned to theAssignee. The priority of pending applications had been claimed herein.

For example, U.S. Patent Application Publication No. US2013/0322818A1discloses an optical coupling device for routing optical signals, whichis in the form of an optical bench having a stamped structured surfacefor routing optical data signals. The optical bench comprising a metalbase having a structured surface defined therein, wherein the structuredsurface has a surface profile that bends, reflects, and/or reshapes anincident light. The base further defines an alignment structure, whichis configured with a surface feature to facilitate precisely positioningan optical component (e.g., an optical fiber) on the base in preciseoptical alignment with the structured surface to allow light to betransmitted along a defined path between the structured surface and theoptical component, wherein the structured surface and the alignmentstructure are integrally defined on the base by stamping a malleablemetal material to form an optical bench.

U.S. Patent Application Publication No. US2015/0355420A1 furtherdiscloses an optical coupling device for routing optical signals for usein an optical communications module, in particular an optical couplingdevice in the form of an optical bench, in which defined on a metal baseis a structured surface having a surface profile that bends, reflectsand/or reshapes an incident light. An alignment structure is defined onthe base, configured with a surface feature to facilitate positioning anoptical component (e.g., an optical fiber) on the base in opticalalignment with the structured surface to allow light to be transmittedalong a defined path between the structured surface and the opticalcomponent. The structured surface and the alignment structure areintegrally defined on the base by stamping a malleable metal material ofthe base. The alignment structure facilitates passive alignment of theoptical component on the base in optical alignment with the structuredsurface to allow light to be transmitted along a defined path betweenthe structured surface and the optical component.

U.S. Patent Application Publication No. US2013/0294732A1 furtherdiscloses a hermetic optical fiber alignment assembly having anintegrated optical element, in particular a hermetic optical fiberalignment assembly including an optical bench that comprises a metalferrule portion having a plurality of grooves receiving the end sectionsof optical fibers, wherein the grooves define the location andorientation of the end sections with respect to the ferrule portion. Theassembly includes an integrated optical element for coupling theinput/output of an optical fiber to optoelectronic devices in anoptoelectronic module. The optical element can be in the form of astructured reflective surface. The end of the optical fiber is at adefined distance to and aligned with the structured reflective surface.The structured reflective surfaces and the fiber alignment grooves canbe formed by stamping a malleable metal to define those features on ametal base.

U.S. Pat. No. 9,213,148 further discloses a similar hermetic opticalfiber alignment assembly, but without an integrated structuredreflective surface.

U.S. Pat. No. 7,343,770 discloses a novel precision stamping system formanufacturing small tolerance parts. Such inventive stamping system canbe implemented in various stamping processes to produce the devicesdisclosed in the above-noted patent publications. These stampingprocesses involve stamping a bulk material (e.g., a metal blank), toform the final overall geometry and geometry of the surface features attight (i.e., small) tolerances, including reflective surfaces having adesired geometry in precise alignment with the other defined surfacefeatures.

U.S. Patent Application Publication No. US2016/0016218A1 furtherdiscloses a composite structure including a base having a main portionand an auxiliary portion of dissimilar metallic materials. The base andthe auxiliary portion are shaped by stamping. As the auxiliary portionis stamped, it interlocks with the base, and at the same time formingthe desired structured features on the auxiliary portion, such as astructured reflective surface, optical fiber alignment feature, etc.With this approach, relatively less critical structured features can beshaped on the bulk of the base with less effort to maintain a relativelylarger tolerance, while the relatively more critical structured featureson the auxiliary portion are more precisely shaped with furtherconsiderations to define dimensions, geometries and/or finishes atrelatively smaller tolerances. The auxiliary portion may include afurther composite structure of two dissimilar metallic materialsassociated with different properties for stamping different structuredfeatures. This stamping approach improves on the earlier stampingprocess in U.S. Pat. No. 7,343,770, in which the bulk material that issubjected to stamping is a homogenous material (e.g., a strip of metal,such as Kovar, aluminum, etc.) The stamping process produces structuralfeatures out of the single homogeneous material. Thus, differentfeatures would share the properties of the material, which may not beoptimized for one or more features. For example, a material that has aproperty suitable for stamping an alignment feature may not possess aproperty that is suitable for stamping a reflective surface featurehaving the best light reflective efficiency to reduce optical signallosses.

U.S. Pat. No. 8,961,034 discloses a method of producing a ferrule forsupporting an optical fiber in an optical fiber connector, comprisingstamping a metal blank to form a body having a plurality of generallyU-shaped longitudinal open grooves each having a longitudinal openingprovided on a surface of the body, wherein each groove is sized tosecurely retain an optical fiber in the groove by clamping the opticalfiber. The optical fiber is securely retained in the body of the ferrulewithout the need for additional fiber retaining means.

PCT Patent Application Publication No. WO2014/011283A2 discloses aferrule for an optical fiber connector, which overcomes many of thedrawbacks of the prior art ferrules and connectors, and further improveson the above noted pin-less alignment ferrules. The optical fiberconnector includes an optical fiber ferrule, which has a generally ovalcross-section for aligning an array of multiple optical fibers tooptical fibers held in another ferrule using a sleeve.

The above inventive concepts are incorporated by reference herein, andwill be referred below to facilitate disclosure of the presentinvention. The present invention is disclosed in connection withexemplary embodiments of hermetic optical fiber feedthrough for hermeticoptoelectronic packages, which includes an optical bench subassemblywith an integrated photonic device.

FIGS. 2A and 2B illustrate one embodiment of a hermetic optical fiberfeedthrough, in the form of an optical bench subassembly 10 thatincludes an optical bench 11 having an integrated photonic device 12 inaccordance with one embodiment of the present invention. In theillustrated embodiment, the photonic device 12 is mounted on a submount14, which is attached to the optical bench 11, at a location inalignment with the optical input/output of the optical bench 11 (seeoptical signal 22 in FIG. 2B).

FIGS. 3A and 3B illustrate more clearly the structure of the opticalbench 11 in the optical bench subassembly 10. In this embodiment, theoptical bench 11 resembles the hermetic multi-fiber alignmentsubassembly disclosed in Assignee's US2016/0016218A1 referenced above.The optical bench supports one or more optical waveguides, which in theillustrated embodiment is a plurality of optical fibers 20 of an opticalfiber cable 21. For the case of multiple fibers, the base 13 of theoptical bench 11 defines a plurality of open grooves 16 supporting theoptical fibers 20, and defines or supports an optical element (e.g., alens, a prism, a reflector, a mirror, etc.). In the illustratedembodiment, the optical element comprises an array of structuredreflective surfaces 17, each corresponding to an optical fiber 20. Thereflective surface may be planar reflective or contoured to be concavereflective (e.g., an aspherical mirror surface) or convex reflective. Inthe illustrated embodiment, the base 13 comprises a composite structure,including an auxiliary portion 30 of a material dissimilar to thematerial of the rest of the base 13 (i.e., the main portion 13′). Thebase 13 including the auxiliary portion 30 are stamped from malleablematerials to form the body geometry and the desired surface features. Inthis case, the auxiliary portion is shaped by stamping a malleablemetallic material to form the array of structured reflective surfaces 17and grooves 18, while the base 13 is stamped from a different malleablemetallic material to form the grooves 16 and the other structures shown.As disclosed in US2016/0016218A1, as the auxiliary portion 17 isstamped, it interlocks with the base 13, resembling a rivet, and at thesame time forming the desired structured features on the auxiliaryportion 30, including the array of structured reflective surfaces 17,and optical fiber alignment grooves 18 for supporting the end sectionsof the optical fibers 20, such that each reflective surface 17 and anend face (i.e., the input/output) of a corresponding optical fiber 20are maintained in precise relationship. In this embodiment, theauxiliary portion 17 and the main portion 13′ are stamped usingdissimilar metallic materials.

The open grooves 16 and 18 may be configured and formed in accordancewith the stamped open grooves disclosed in U.S. Pat. No. 8,961,034,which clamps the optical fibers in securely in the groove withoutrequiring additional securing means (e.g., no epoxy, etc.). In theillustrated embodiment, a cover 15 is provided to cover the base 13without covering the structured reflective surfaces 17. A hermeticsealing epoxy (e.g., glass epoxy) is applied to fill the spaces aroundthe sections of the optical fibers 20 in the cavity 19 between the cover15 and the base 13, to form a hermetic seal to make the optical bench 11a hermetic feedthrough, which can be used with a optoelectronic packagein a similar function as the hermetic feedthrough 502 in FIG. 1A, exceptthat the optical bench 11 has a photonic device integrated thereon toform the optical bench assembly 10 in accordance with the presentinvention. Further elaborations of similar hermetic feedthroughstructures may be found in US2013/0294732A1.

FIGS. 4A and 4B illustrate another embodiment of an optical bench 11′,which is similar to the optical bench 11 in FIGS. 3A and 3B, with theexception of the fiber cable 21. In this embodiment, the optical bench11′ is provided with a demountable connection in the form of a ferrule30. Instead of an optical fiber 21 extending away from the optical bench11′, the ferrule 30 supports the rear end sections of short sections ofoptical fibers 20, with the distal front end sections of the opticalfibers supported by the grooves 16 and 18 within the optical bench 11′.The ferrule 30 may be structured to have a generally oval cross-section,as disclosed in WO2014/011283A2. A sleeve (not shown) can be used tocouple to, for example, an optical fiber cable (e.g., a patch cable)that is terminated with a similar ferrule. In this embodiment, if theconnecting optical fiber becomes defective, it can be disconnected andreplaced, without having to replace the entire optoelectronic package towhich the optical bench 11′ is permanently or fixedly attached.

Turning now to the photonic device, in the illustrated embodiment ofFIGS. 2A and 2B, the photonic device 12 is mounted on a submount 14 toform a photonic device assembly 23. The submount 14 may be provided withcircuits, electrical contact pads, circuit components (e.g., a driverfor VCSEL, a TIA for a PD), and other components and/or circuitsassociated with the operation of the photonic device 12.

FIGS. 6A to 6C illustrate the sequence of assembly of a hermeticoptoelectronic package. FIG. 6A depicts assembly of a photonic device (atransmitter or a receiver or a transceiver) assembly; FIG. 6B depictsassembly of the photonic device assembly to the optical bench and activealignment; FIG. 6C depicts assembly of the hermetic optoelectronicpackage.

Referring to FIG. 6A, in the case where the photonic device 12 is atransmitter, such as a VCSEL, it is mounted on the submount 14, alongwith a driver chip. The VCSEL may be wirebonded to the circuit on thesubmount 14. Test may be performed to confirm that the VCSEL isoperative to transmit an optical signal after assembly. In the casewhere the photonic device 12 is a receiver, such as a PD, it is mountedon the submount 14, along with a TIA chip. The PD may be wirebonded tothe circuit on the submount 14. Test may be performed to confirm thatthe PD is operative to receive an optical device and output anelectrical signal after assembly. In the case of a transceiver, theabove procedures are combined to test the separate receiving andtransmitting functions. The photonic device 12 may include a pluralityof receivers, transmitters and/or transceivers mounted on the submount14.

Referring to FIG. 6B, the submount 14 of the photonic device assembly isattached to the opposing surface of the base 13 of the optical bench 11,at a position in which the photonic device 12 is in optical alignmentwith the optical bench 11, where the input/output of the photonic device12 is optically aligned with the output/input of the optical bench 11,so that the optical path 22 achieves the desired optical couplingefficiency between the photonic device 12 and the optical fiber 20. Inthe illustrated embodiment in FIG. 2B, the optical path 22 is betweenthe input/output end face of an optical fiber 20 and the output/input ofa corresponding optical device 12, which is bent and reshaped by thereflective surface 17 (e.g., an aspherical mirror surface). Morespecifically in the illustrated embodiment, the optical path is in adirection out of the plane of the base 13, which is generallyperpendicular to the plane of the base 13. As shown in FIG. 2B, theplane of the submount 24 is parallel to the plane of the base 13. Aframe 32 is provided as a spacer between the submount 14 and theopposing surface of the base 13, to provide a space to accommodate thephotonic device 12 between the submount 14 and the base 13. In theillustrated embodiment, there is an array of four reflective surfaces 17corresponding to an array of four optical fibers 20.

The photonic device 12 may be passively aligned with the optical bench11 (e.g., by relying on alignment indicia (not shown) provided on thebase of the bench 11). Alternatively, the photonic device 12 and theoptical bench 11 may be actively aligned by passing an optical signalbetween the optical waveguide (i.e., the optical fibers 20) in theoptical bench 11 and the photonic device 12, and measuring the strengthof the optical signal in the optical path to determine the opticalcoupling that indicates an optically aligned state. The photonic device12 (e.g., a VCSEL and/or PD) can be activated to allow for activealignment with the optical fibers supported in the optical bench 11,without having to rely on the other components within the optoelectronicpackage to which the optical bench subassembly 10 is to be installed.For example, in the case where the photonic device 12 is a transmitter(e.g., a VCSEL), it is energized to emit light to the reflective surface17 to be directed to the end face of the corresponding optical fiber 20.The strength of the optical signal transmitted via the reflectivesurface 17 and through the corresponding optical fiber is measured todetermine optical coupling between the transmitter and the optical bench11. In the case where the photonic device is a receiver (e.g., PD), anoptical signal is supplied through the optical fiber, which is reflectedby the reflective surface to a corresponding receiver. The extent ofoptical coupling between the optical fiber and the receiver can bedetermined from the electrical output of the receiver (which correspondsto strength of the optical signal received), so as to identify thealigned state. The active alignment process involves moving the photonicdevice 12 in the plane of the submount 14, with respect to thereflective surfaces 17, while the optical coupling efficiency isdetermined for the alignment point. To facilitate electrical connectionto undertake active alignment, electrically conductive pads are providedon the surface of the submount that face away from the base 13.

Upon achieving desired optical alignment, the submount 14 of thephotonic device 12 is fixedly attached to the base of the optical bench,e.g., by laser welding, soldering or epoxy.

After assembly of the optical bench subassembly 10, it can be burned-into eliminate early-life failures and further functionally tested.

The foregoing embodiments of the optical bench subassembly 10 thatinclude the integrated photonic device 12 are hermetic feedthrough withthe integrated photonic device 12.

Referring to FIG. 6C, and as shown in FIG. 2B, upon completing theassembly of the optical bench subassembly 10, it is hermeticallyattached to an optoelectronic package 500′ (e.g., by soldering), whichcan be similar to the package 500 in FIG. 1A, except that the photonicdevice 12 is integrated in the optical bench subassembly 10, in opticalalignment with the optical bench 11. The optoelectronic package 500′ ispopulated with various components (e.g., ICs, chips, submounts, circuitboards, etc.). The optical bench subassembly 10 as a hermeticfeedthrough is inserted through the opening of the snout 50 in thesidewall of the housing 501′ of the package 500′ and hermetically sealed(e.g., by soldering). As compared to the situation in FIG. 1B, theposition of this feedthrough with respect to the package 500′ is not ascritical since there is no optical alignment required between thefeedthrough and an external photonic device within the package 500′. Asshown in FIG. 2B, the submount 14 may be solder bonded to a printedcircuit board 39 (which could be a flexible printed circuit board)within the package 500′, with vias 36 provided through the substrate ofthe submount 14 to connect to the photonic device 12 on the other sideof the submount 14. A ball-grid array (BGA) with micro solder balljoints may be configured on the submount 14. Other electricalconnections may include the optical bench subassembly 10′ in theembodiment of FIG. 5, in which wrap-around traces 38 provided on theside of the submount 14′ are electrically connected to a circuit board(not shown) in the package 500′ by a wire bond or flex circuit joint 37.Alternatively, spring pins (not shown) may be configured to make theelectrical connections between the submount and a printed circuit boardin the package 500′. These electrical connections absorb error motionand stress due to thermal expansion/contraction, which would not affectthe optical alignment between the photonic device that is integratedonboard the optical bench in the optical bench subassembly.

FIG. 7 illustrates the hermetic feedthrough/optical bench subassembly 10as installed in the hermetic optoelectronic package 500′. The otherelectronics and circuit components are omitted from view in FIG. 7. Thehermetic cover of the hermetic optoelectronic package 500′ is alsoomitted from view.

After assembly of the optical bench subassembly 10 to the hermeticoptoelectronic package 500′, the package 500′ can be burned-in toeliminate early-life failures and further functionally tested.

Given the present invention preassemblies optical elements andcomponents and photonic devices precisely in an optical benchsubassembly prior to assembling into the larger optoelectronic package,the optical bench subassembly can be functionally tested, includingburn-in tests, in a subassembly level, outside of an optoelectronicpackage, thus reducing waste of more expensive packages (which includesexpensive circuit components, such as ICs, etc.) arising from earlyfailure in the photonic devices installed therein. The active alignmentprocess for the optical bench subassembly is much easier. Further, muchsmaller and more robust structural loop is present between the opticalbench and the photonic device. Thus overall higher yield, higherreliability and lower manufacturing costs can be achieved foroptoelectronic packages incorporating the hermetic feedthrough inaccordance with the present invention.

While the invention has been particularly shown and described withreference to the preferred embodiments, it will be understood by thoseskilled in the art that various changes in form and detail may be madewithout departing from the spirit, scope, and teaching of the invention.Accordingly, the disclosed invention is to be considered merely asillustrative and limited in scope only as specified in the appendedclaims.

1. (canceled)
 2. A method of forming a photonic subassembly, comprising:(a) providing a photonic device subassembly comprising: a submounthaving electrical contacts at a bottom surface thereof; and at least aphotonic device mounted on a top surface of the submount; (b) providinga hermetic optical bench subassembly for routing optical signalcomprising: an optical bench comprising a base, wherein at least astructured surface and at least one alignment structure are defined on asurface of the base, wherein the structured surface has a surfaceprofile that reshapes and bends an incident light; and at least oneoptical fiber positioned with the alignment structure in opticalalignment with the structured surface, wherein the optical fiber ishermetically sealed to the base; (c) assembling a photonic subassembly,comprising: aligning the photonic device in the photonic devicesubassembly as provided in (a) in optical alignment to the structuredsurface in the hermetic optical bench subassembly as provided in (b);fixedly attaching the submount in the photonic device subassembly to thebase in the hermetic optical bench subassembly upon optical alignment ofthe photonic device in the photonic device subassembly to the structuredsurface in the hermetic optical bench subassembly.
 3. The method ofclaim 2, wherein the structured surface and the alignment structure areintegrally defined on the base by stamping a malleable metal material ofthe base.
 4. The method of claim 3, wherein the optical signal istransmitted along the defined optical path between the photonic devicein the photonic device subassembly and the optical fiber in the hermeticoptical bench subassembly via the structured surface without relying ona refractive optical element between the optical fiber and thestructured surface.
 5. The method of claim 3, wherein the structuredsurface conforms to an aspheric reflective surface profile.
 6. Themethod of claim 5, wherein the aspheric reflective surface is structuredto reshape light to couple input/output of the optical fiber and thephotonic device without relying on a refractive optical element betweenthe input/output of the optical fiber and photonic device.
 7. The methodof claim 2, wherein an array of structured surfaces and a plurality ofalignment structures are defined on the base, and wherein an array ofoptical fiber are positioned with the alignment structures to opticallyalign the optical fibers with corresponding one of the structuredsurfaces.
 8. The method of claim 7, wherein the hermetic optical benchsubassembly further comprising a cover hermetically attached to the baseto hermetically seal a space around a section of the array of theoptical fibers, wherein the cover does not extend to cover thestructured surface, thereby to result in a hermetic feedthrough.
 9. Themethod of claim 2, wherein the photonic subassembly is assembled in (c)with the submount in the photonic device subassembly attached to thebase in the hermetic optical bench subassembly, with the top surface ofthe submount facing the structured surface in the optical bench, andwith the photonic device in optical alignment with the structuredsurface.
 10. The method of claim 9, further comprises testing thephotonic device subassembly prior to assembling the photonic subassemblyin (c).
 11. A method of forming a hermetic optoelectronic packagecomprising providing a photonic subassembly as assembled in claim 2,further comprising: (d) providing a hermetic package comprising: ahousing having an opening sized to receive the hermetic optical benchsubassembly in the photonic subassembly; and a circuit board within thehousing, wherein the circuit board comprises electrical circuits andelectronic components populated on the circuit board; and (e)hermetically assembling the photonic subassembly to the hermetic packageas provided in (d), comprising: positioning a section of the hermeticoptical bench subassembly in the photonic subassembly at the opening inthe housing of the hermetic package; electrically attaching theelectrical contacts at the bottom surface of the submount in thephotonic device subassembly to the electrical circuits on the circuitboard; and hermetically attaching the section of hermetic optical benchsubassembly at the opening to the housing.
 12. The method of claim 11,further comprises functionally testing the photonic subassembly asassembled in (c) prior to assembling to the hermetic package in (e). 13.The method of claim 11, wherein the photonic subassembly as assembled in(c) is functionally tested at a subassembly level, including burn-intests prior to hermetically attaching the section of the hermeticoptical bench subassembly at the opening to the housing.
 14. A photonicsubassembly, comprising: a photonic device subassembly, which comprises:a submount having electrical contacts at a bottom surface thereof; andat least a photonic device mounted on a top surface of the submount, ahermetic optical bench subassembly, which comprises: an optical benchcomprising a base, on which at least a structured surface and at leastone alignment structure are defined on the base, wherein the structuredsurface has a surface profile that reshapes and bends an incident light;at least one optical fiber positioned with the alignment structure inoptical alignment with the structured surface, wherein the optical fiberand the base are hermetically sealed, wherein the photonic device in thephotonic device subassembly is in optical alignment to the structuredsurface in the hermetic optical bench subassembly, and wherein thesubmount in the photonic device subassembly comprises electricalcontacts for mounting to an external circuit, and wherein the submountin the photonic device subassembly is fixedly pre-attached to the basein the hermetic optical bench subassembly upon optical alignment of thephotonic device in the photonic device subassembly to the structuredsurface in the hermetic optical bench subassembly prior to mounting thesubmount to the external circuit.
 15. The photonic subassembly as inclaim 14, wherein the base is an integral body on which the structuredsurface and the alignment structure are integrally defined on the bodyby stamping a malleable metal material of the body.
 16. The photonicsubassembly as in claim 15, wherein the optical signal is transmittedalong the defined optical path between the photonic device in thephotonic device subassembly and the optical fiber in the hermeticoptical bench subassembly via the structured surface without relying ona refractive optical element between the optical fiber and thestructured surface.
 17. The photonic subassembly as in claim 16, whereinthe structured surface conforms to an aspheric reflective surfaceprofile.
 18. The photonic subassembly as in claim 14, wherein an arrayof structured surfaces and a plurality of alignment structures aredefined on the base, and wherein an array of optical fiber arepositioned with the alignment structures to optically align the opticalfibers with corresponding one of the structured surfaces.
 19. Thephotonic subassembly as in claim 18, wherein the hermetic optical benchsubassembly further comprising a cover hermetically attached to the baseto hermetically seal a space around a section of the array of theoptical fibers, wherein the cover does not extend to cover thestructured surface, thereby to result in a hermetic feedthrough.
 20. Thephotonic subassembly as in claim 14, wherein the submount in thephotonic device subassembly is attached to the base in the hermeticoptical bench subassembly, with the top surface of the submount facingthe structured surface in the optical bench, and with the photonicdevice in optical alignment with the structured surface.
 21. A hermeticoptoelectronic package comprising the photonic subassembly as in claim14, further comprising: a hermetic package, which comprises: a housinghaving an opening sized to receive the hermetic optical benchsubassembly in the photonic subassembly; a circuit board within thehousing, wherein the circuit board comprises electrical circuits andelectronic components populated on the circuit board, wherein theelectrical contacts at the bottom surface of the submount in thephotonic device subassembly is electrically attached to the electricalcircuits on the circuit board, and wherein the photonic subassembly,with the photonic device in the photonic device subassembly in opticalalignment to the structured surface in the hermetic optical benchsubassembly, is hermetically attached to the hermetic package with asection of the hermetic optical bench subassembly in the photonicsubassembly at the opening in the housing of the hermetic package.